A travel control device is known in which, when another vehicle is detected at the left side of a subject vehicle, the travel position of the subject vehicle is set at the right side from a normal position and when another vehicle is detected at the right side of the subject vehicle, the travel position of the subject vehicle is set at the left side from the normal position (See JP2013-091401A).
In the above technique, however, if another vehicle comes close to the subject vehicle and comes away from the subject vehicle while the subject vehicle and the other vehicle are traveling side by side, detection and non-detection of the other vehicle are repeated, which may cause hunting in control when performing travel control for the subject vehicle to the other vehicle.